In a torsion beam suspension, in general, a torsion beam is arranged between a pair of right and left trailing arms arranged in a front-rear direction of a vehicle, and both end portions of the torsion beam are welded to the trailing arms.
The trailing arms joined to both ends of the torsion beam each have an upper member and a lower member. The upper member and the lower member form a hollow structure, and the upper member is continuously formed with the torsion beam (See Patent Literature 1).